When during drilling in rock or concrete, the drill dust or drillings obtained have to be transported out of the drillhole by means of a spiral shank. Fastening regulations for anchorages by means of dowels prescribe that the drill dust be removed completely from the drillhole. This can present difficulties, however, since, on the one hand, the drill dust can be caked in the drillhole and, on the other hand, suitable means for removing the drill dust, such as, for example, compressed air or the like, is not always available. Nevertheless, an anchorage by means of a dowel/screw connection depends essentially on the removal of the drill dust from the drillhole.
The outside diameter of the spiral shank of a conventional rock drill is always less than the nominal diameter of the drilling tool which is formed by the outside diameter of the carbide cutter. The spiral shank therefore cannot fully ensure that the drill dust is scraped off completely from the inner wall of the drillhole.
German Offenlegungschrift 2,403,722 discloses a drilling tool having a push-on feed coil composed of a helically formed wire part made of rubber, synthetic rubber, pressed material or the like, the outer edge of the feed coil being narrow and flexible, so that a certain brush effect and consequently a cleaning of the drillhole will be obtained by means of these regions.
A disadvantage of this known drilling tool is the construction of these allegedly brushing members which is to be formed by a mere reduction of the wall thickness of an otherwise conventional feed coil. This would seem, in practice, to lead to a rapid wear of these regions, because they are not true brush-like members, but means which at most exert a certain scraping effect.